Device for automatically stopping the fall of personnel working high above ground

ABSTRACT

The device comprises, inside a case, a tightening cam (7) hinged about an axis (8) such that, unused, it does not engage a belaying rope (2) passing through the case and, when the device is subjected to a set acceleration downwards, it pivots towards the rope (2) to tighten it to the case with self-tightening effect. On the cam (7) is mounted a detecting roller (10) which co-operates with the rope (2) when the cam (7) is unused. A spring actuated (13) friction piece (12), at a certain rotational speed of the roller (10), subjects it to a resisting moment which triggers off the pivoting of the cam (7) in the tightening direction. A lever (15), to which the user is linked, engages in a unidirectional manner the cam (7) to push it in tightening position if the user falls. The device simultaneously triggers off several tightening effects in case of a fall.

FIELD OF THE INVENTION

The present invention concerns an individual anti-fall protective deviceand more particularly a device designed to automatically stop the fallof a person working above ground level.

BACKGROUND OF THE INVENTION

There are several individual anti-fall protective devices sliding on asupport, such as a rope, orientated vertically and fixed at its upperportion.

These devices are connected by a head rope to an operator when they areintended to protect the latter from falling.

To this effect, these devices have been designed so as to slide upwardsand downwards along the support and able to lock on the latter shouldthe operator fall.

Some of the models of these devices are complicated and tighten anelement on the support under the dynamic effect caused by a fall of theoperator connected to the device.

The most advanced models do have the drawback of comprising a largenumber of fragile elements. Most of these devices mean that constantvigilance is required to ensure they are clean as they are sensitive tothe presence of debris and dust which adversely affect their operationalefficiency.

The U.S. Pat. No. 4,923,037 describes an automatic anti-fall stoppagedevice able to move along a vertical support. This device includes amounted toothed wheel for rotating inside its housing joined to theinside of an external housing and is elastically stressed in a directionapplying the toothed wheel against the support passing into a verticalchannel fitted at the front portion of the external housing. When thedevice moves along the support, the toothed wheel is rotary-driven viaits friction on the latter. If the fall speed of the device along thesupport reaches a predetermined value, the corresponding speed ofrotation of the toothed wheel triggers a centrifugal clutch mechanismwhich stops rotation of the toothed wheel. The friction between thesupport and the stopped toothed wheel then causes the housing to pivotin a direction ensuring the tightening of the support between thetoothed wheel and the external housing and locking of the device on thesupport.

In this device, where the toothed wheel is used both to detect themoving speed of the device and as a tightening element, the centrifugalclutch system, which triggers automatic tightening, is a costly andfragile element sensitive to dust.

The French patent published under the N^(o) 2574511 also concerns adevice for automatically tightening on a safety rope. This deviceincludes a roller able to move along a ramp between a lower restposition, in which it is distanced from the safety rope, and an upperposition where it tightens the rope so as to lock the device on thelatter. A lever, hooked to the head rope connected to the user, engagesthe mobile roller under the dynamic effect of a fall of the user so asto bring it to a position enabling it to be tightened.

Owing to the lightness of the tightening roller able to rise along theguiding ramp under the effect of jerks or vibrations, this device isextremely sensitive to poorly controlled functioning and is likely tofunction erratically.

SUMMARY OF THE INVENTION

The aim of the present invention is to provide an automatic anti-falldevice avoiding the drawbacks mentioned above of known types of devicesand has the advantages of simplicity, sturdiness and improvedefficiency.

To this end, the device is embodied by a small number of elements havingsimple shapes cooperating together to simultaneously implement threemodes for triggering the tightening effect on the support:

via the acceleration of a detector element situated on the tighteningelement and which starts its tightening movement,

via the embodiment of the tightening element in the shape of atightening cam mounted in such as way so that the position of its centreof gravity with respect to its spin axis provokes an inertial effectshould the device be suddenly stressed downwards which activatestightening of the cam,

via the action of a lever under the effect of the load.

According to the invention, the automatic anti-fall device, which slideswithout requiring any additional operation onto a safety support fixedat a point situated above said device connected to the user or a load,is of the type comprising an element for tightening the safety supportand an element for detecting an acceleration threshold or the movingspeed of the safety support with respect to the device. It ischaracterised in that the detector element, constituted by a roller oran equivalent rotary element, and the tightening element are separateelements, the detecting element being mounted on the tightening elementand driving the latter in the direction of tightening under the effectof a resistant torque with a specific level opposing the rotation of theroller, said resistant torque being generated by a device secured to thetightening element and acting on the basis of a specific threshold ofthe speed or acceleration of the safety support in the device.

The device generating the resistant torque is preferably formed of afriction piece or cam applied against the roller under the effect of aspring pressing on the safety element and generating a resistant torqueincreasing with the speed of the support in the device up to a thresholdgreater than an opposing resistant torque of the cam.

The tightening element can be constituted by a self-tightening campivoting with the safety support, the detecting roller being situated soas to be in contact for cooperating with the support for a specificposition of the cam when no tightening stress is applied to the latter,and so as to no longer be in contact as soon as the cam starts itstightening action.

The centre of gravity of the cam is placed with respect to the spin axisof the latter so as to stress this cam in association with its weight inthe direction of its untightening when there is no given acceleration ofthe device downwards, and so as to stress said cam in the oppositedirection when there is acceleration of the device from an accelerationthreshold to activate tightening.

According to the invention, so as to embody the third tightening effect,the device comprises a load activation lever cooperatingunidirectionally with the cam by means of a stop so that this cam canonly be activated by this lever in a direction provoking tightening.

According to one preferred embodiment, a linking spring mounted on thehinge pin common to the lever and cam comprises two ends, one beingapplied at one point of the box of the device and the other beingapplied to the cam so as to stress it in rotation in the untighteningdirection and thus constantly apply it to contact of the lever in theabsence of any positive action for stopping the latter at an upperposition simultaneously with a phenomenon activating tightening of thecam.

The weight of the cam associated with the positioning of its centre ofgravity is calculated so as to neutralise the action of the spring totighten the entire device under the effect of a specific downwardsacceleration.

In all these cases, the starting of rotation of the cam in thetightening direction results in the automatic continuation of thetightening movement by virtue of the configuration of the facecooperating with the rope, thus provoking a self-tightening phenomenonuntil full locking.

The activation lever is configured and positioned in such a way as to beable to activate or accompany the cam as regards its entire travel untilthe rope is fully locked.

BRIEF DESCRIPTION OF THE DRAWINGS

So as to clearly understand the device of the invention, there nowfollows a description given by way of example of a preferrednon-restrictive embodiment with reference to the accompanying drawing onwhich:

FIG. 1 is a partially vertical sectional side view of an automaticstoppage device of the present invention and shown in its rest positionenabling it to move along the safety rope.

FIG. 2 is a view of the device of FIG. 1 in its stoppage position aftertriggering of tightening by moving the pivoting lever.

FIG. 3 is a view of the device of FIG. 1 in its stoppage positionwithout triggering of tightening having been controlled by the lever,and

FIG. 4 is a view similar to FIG. 2, but showing the device locked in adeliberate manual stoppage position (parking).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawing, the automatic stoppage device, generallydenoted as 1, is intended to tighten a vertical safety rope 2 whichtraverses it. The rope 2 is fixed at its upper end and is provided witha ballast (not shown) at its lower end.

The device 1 comprises a box made up of two lateral plates 3 (only onevisible on the drawing) connected by braces 4 with one frontal wall 5and one rear wall 6.

Housed inside the box is a tightening cam 7 mounted to pivot around ahorizontal pin 8 borne by the plates 3. Towards its front portion, thecam 7 has an arched tightening surface 9 and comprises at its frontupper portion a detection roller 10 mounted loose on a transverse axis11 borne by the cam 7.

Circulating in the space provided between the internal face of thefrontal wall 5 and the front end of the cam 7 is a safety rope 2 whoserelative movement with the device 1 drives the detecting roller 10 inrotation. The rotation of the roller 10 is halted by a friction piece 12which engages the periphery of this roller under the stress of a spring13 resting on the body of the cam 7. From a specific threshold of thespeed of rotation of the roller, the force of the spring 13 is selectedso as to apply to the roller a resistant torque with a specific levelopposing the rotation of the roller and partially rendering integral theroller 10 and the cam 7.

A spring 14 wound onto the shaft 8 and pressing partly on the cam 7 andpartly on the rear wall 6 acts on the cam 7 so as to keep the latter inits position shown on FIG. 1 where its tightening surface 9 does notengage the safety rope 2 and where the detecting roller 10 cooperateswith this rope 2.

A bent lever 15, joined at its intermediate portion around the pin 8,has one arm which projects through an aperture 16 of the rear wall 6,whereas with the upper position of the lever 15 stopped against the wall6 (as shown on FIG. 1), the end 17 of its other arm is used as a stopfor the cam in its untightening position.

The disposition of the roller 10 on the cam 7 has been provided so that,when the cam is in a stop position against the lever 15, the roller 10comes into contact with the rope 2.

The disposition of the cam 7 is such that its centre of gravity isplaced with respect to the spin axis 8 so as to stress this cam in theuntightening direction should there be no given acceleration of thedevice downwards, and to stress this cam in the opposite direction bymeans of inertia where this acceleration takes place on the basis of aspecific threshold of the latter, thus then neutralising the action ofthe spring 14.

The arm of the lever 15, which traverses the aperture 16, has at its endan opening 18 for hooking the spring snap (not shown) of a ropeassociated with a worker.

It is to be noted that the lever 15 only controls movement of the cam 7via a stop in the tightening direction. This avoids any ill-timeduntightening by any ill-timed or clumsy manoeuvre of the lever.

The functioning of the device is as follows: assuming that it issituated in its non-tightening position shown on FIG. 1, because of theweight of the device 1, the projecting arm of the lever 15 is in theupper position and is situated at a level lower than the user.

As indicated earlier, the cam 7 is situated in its untightenned positionin support against the stop portion 17 of the lever 15, itself in a stopposition against the wall 6 under the combined effect of the weight ofthe cam and the spring 14. The device 1 then slides freely along thesafety rope 2 upwards or downwards, depending on the movement of theuser, thus driving the roller 10 in rotation.

Should the user fall, a triple effect for triggering tightening of thecam 7 is effected as follows:

a) the sudden acceleration of the falling movement of the device 1 alongthe rope 2 is immediately detected by the roller 10 whose speed ofrotation increases until the resistant torque to which it is subjectedsurmounts the opposing resistant torque of the cam 7. This cam thenpivots clockwise around the spindle 8 so that its tightening surface 9engages the rope 2 and locks it against the wall 5, thus immobilisingthe device.

As can be seen on FIG. 2, as soon as the cam 7 starts to move to tightenthe rope 2, the detecting roller 10 stops cooperating with the latter,and in its maximum tightening position, the cam 7 engages a stop formedof one of the braces 4 so as to control tightening.

b) Because of the inertia of the cam 7, the sudden stressing of thedevice 1 downwards due to the fall triggers a pivoting movement of thelatter in a direction which initiates tightening of the rope 2.

c) Under the effect of the free fall load connected to its end 18, thelever 15 pivots clockwise through its stop portion 17 acting on the cam7 so as to bring it into its tightening position. The lever 15accompanies the cam 7 for its entire tightening travel until the rope 2is fully locked.

As the lever 15 pivots freely on the spindle 8, an accidentalimmobilisation of the latter in its rest position shown on FIG. 1 couldonly oppose one of the two effects described above at a) and b) or thetwo together to carry out tightening.

As shown on FIG. 4, a device for locking the lever 15 in a lockingposition and formed, for example, of a catch 19 joined at 20 to the boxand engaging the rear face of the lever 15, is able to keep the cam 7 inthe rope 2 locking position, thus being used as a parking brake.

The box of the device comprises an opening element (not shown on thedrawing) so that the closed position of the box is locked by twoseparate elements, thus requiring the intervention of two successivedeliberate operations to open this box.

For the requirements of the description of the present invention, a ropehas been adopted as a support for the device and a cam has been adoptedas a tightening element whose tightening throat can be profiled so as tocorrespond to the section of the rope by means of the self-tightening ofthis rope. For the same needs, a roller has been used as a detector.However, without departing from the context of the invention, the samesystem could be constructed according to the state of the Art so as tofunction as a support formed of a metallic cable or rigid profile.

What is claimed is:
 1. An automatic anti-fall device able to slide,without requiring any additional operation, onto a safety support fixedto a point situated above the anti-fall device, said anti-fall devicefor connection to a user or a load and comprising:(a) a cam pivotallymounted within a box of the anti-fall device said box having a passagefor receiving the safety support, said cam positionable in anon-tightening position against the safety support when a relativemovement between the anti-fall device and the safety support is under athreshold value of acceleration or speed, and said cam being able topivot in one direction of rotation to tighten against the safetysupport; (b) a detecting roller mounted to rotate on said cam so as tocooperate with said safety support, when said cam is in itsnon-tightening position, with a rotating speed proportional to the speedof relative movement between the anti-fall device and the safetysupport; and (c) a friction system comprising a movable friction piecemounted on said cam and a spring applying said movable friction pieceagainst the periphery of said detecting roller, so as to apply to saiddetecting roller a resistant torque opposing the rotation of thedetecting roller and, when said threshold value is reached, renderingsaid detecting roller and said cam integral so as to rotate said cam inits tightening position.
 2. Device according to claim 1 wherein a travelof the cam towards its non-tightening position is limited by a stopwhich defines a position of the detecting roller enabling said detectingroller to be driven by a relative movement of the safety support, aspring leaning against said box of the anti-fall device acts on this camso as to urge the cam towards its non-tightening position until itreaches a stop position.
 3. Device according to claim 2 wherein thecenter of gravity of the cam is placed with respect to a spindle of thecam so as to urge said cam, together with the action of its weight,towards its non-tightening position in the absence of a givenacceleration of the anti-fall device downwards, and so as to urge saidcam in an opposing direction in the presence of said given acceleration,from a threshold of said given acceleration, up to a sufficient extentto neutralize the spring action applied to the cam and to begin aself-tightening action.
 4. Device according to claim 2 comprising a loadactivated lever cooperating unidirectionally with the cam through saidstop so that an activation of said cam by the load activated lever canonly take place in a direction ensuring tightening.
 5. Device accordingto claim 4 wherein said stop limiting the travel of the cam towards thenon-tightening position is ensured by the load activated lever throughan abutment of said load activated lever on said box of the anti-falldevice so that, in association with the spring action urging the cam, acontinuous contact between the load activated lever and the cam isobtained in the absence of any action applied to the load activationlever for preventing this lever form following the cam in a tighteningmovement.
 6. Device according to claim 1 which comprises a lockingelement, able to lock the cam in its tightening position.